I've mentioned it before that my board repair skills are decent, but not to the point where I can fix every board I come across. Centipede seems to be one of those boards that I either figure out and feel really good about my skills or spend a half day trying to fix one and ask myself why I even bother trying to fix them. Here's are few repairs I made recently as well as some from way back. Enjoy!
One troubleshooting note on these, always put the game in test mode if it isn't working, ram failures are common and the self-test does a half-decent job of telling you what ram is bad.
Nothing on boot (1/18/18)
- 12 mhz clock signal looked good, but no 6mhz clock on test point.
- Replaced 74LS163 at P2 and the board booted right up.
Nothing on boot (5/30/17)
- No clock signal, 2N3904 at Q1 was bad. Crystal was damaged as well, replaced the crystal.
- Board boots but reports ram error, three beeps, K7 is bad?
- Replaced 2101 at K7, board still beeping three times.
- Removed and socketed three other rams that were replaced at one point but weren’t socketed, repair worked looked decent, but wasn’t taking any chances. I’ve seen traces damaged in the past from stuff like this.
- Still beeping three times, further probing showed floating outputs at K7. Also discovered 2H signal at pin 117 on rams K7, L7 and M7 was missing.
- Checked continuity from N7, not there, repaired broken trace (that I couldn’t see) to fix the problem.
- Board now beeps ten times. Removed and replaced 2101 at N5 to fix the boardset.
Solid screen on boot (5/26/17)
- Reset button wasn’t working, replaced it.
- Reset signal was stuck low.
- VBLANK was WATCHDOG was not pulsing
- Outputs on P3 (1V, 2V, 4V and 8V) were dead, clock signal input was good. Replaced 74LS163 at P3 and got some random garbage on screen. Piggybacking this chip did the same thing )showed garbage on the screen).
- Board is now watchdogging.
- Board passes long ram test on 2114 program ram using Fluke 9010a.
- Program Rom 310 at J1 tests bad using Fluke 9010a, install a new program rom and board is now running.
- During testing board started acting up, blank screen on boot sometimes, random garbage. Pressing on program roms and 6502 helped. Replaced sockets on 6502 and program roms and board is all better again.
Blue Screen (4/19/17) – Clean boardset that booted to a blue screen and that was about it. Swapped 6502, no change, put game into test mode and it beeped twice, indicated bad 2114 ram at F2. Removed, socketed and installed working 2114 ram to fix the boardset.
Plays, minor Video Issues (4/19/17) – I didn’t even realize the game had an issue until I played a game. Some of the centipede graphics were jumpy and other minor issues. Test mode reported a bad 2101 ram at L5 (six beeps), replaced this ram to fix the problem.
Plays, but Garbage Letters on Screen (2/28/12) – Put game in test mode and it reported Ram K7, replaced this and it then reported Ram M7 bad. It looked like M7 was already replaced (but not socketed). Removed M7, installed socket, fixed broken trace from prior repair and put a new 2101 Ram and the board worked.
Plays, but Garbage Letters on Screen (2/29/12) – Put game in test mode and it reported bad Ram K7, replaced this and it then reported Ram L5 bad. Replaced Ram L5 and the board came up fine.
Video Issues, Zeros on Screen, No Sound (2/28/12) – Game would play, but there were zeros on the first screen. Reseating the character roms and the problem went away. There was still no sound, checked around LM324 amp and found that the output was dead (input was dead too, but I assume the LM324 was causing that). Replaced LM324 and sound came back.
No Sound (2/29/12) – Didn’t even bother troubleshooting, just replaced LM324 amp and the problem was fixed.
Garbage on Screen (2/29/12) – Board booted with some random characters on screen. Tried test mode, but realized test switch was stuck on, replaced test switch, still garbage, nothing from test mode. Watchdog was barking, tried disabling and test mode, but nothing. Swapped out four program roms (307-310) and the game came up with no background graphics. Tried test mode and it reported a bad Pokey at C3 and bad ER-2055 IC. Replaced both of these and the board worked fine.